While displaying Sub Totals in a Cross Tab, is it possible to view them only for Rows and not for columns or vice versa ??

Jim Wahl's answer is the way to go.

A workflow that I use is:

1) Add all the subtotal using using Analysis > Add all Subtotals as shown in this image:

2) Go to the pill on the rows or columns shelf and take off the subtotal I don't want. 

There might be another way.